Subject: Space-tech Digest #61 Contents: Lou Adornato Booster concepts [1st stage catapults] Marc Ringuette Re: Booster concepts Joe Pistritto Re: Booster concepts S Schaper Re: Booster concepts Lou Adornato Re: Booster concepts Marc Ringuette Re: Booster concepts Bruce Dunn Endcapping evacuated tunnels Henry Spencer Re: Endcapping evacuated tunnels Paul Dietz Re: Endcapping evacuated tunnels Jim Meritt Re: Endcapping evacuated tunnels Joe Pistritto Asteroid Prospector Henry Spencer Re: Asteroid Prospector ------------------------------------------------------------ Date: Tue, 29 May 90 13:55:20 CDT From: Lou Adornato To: space-tech@CS.CMU.EDU Subject: booster concepts Fellow Technocrats; (sorry if some of you get this twice, I sent out an earlier version of this by mistake) I was recently browsing throught some old books, and I ran across a sketch for one of the Peenemunde systems that was never built. I'd like to toss an updated version of the idea out for discussion. The basic idea is to use a catapult system to act as a first stage of a booster. In the peenemunde sketch, the catapult was an iron rail, and the boost came from a captive V-2 engine (in essense, it was a rocket sled). The captive first stage could be recovered and, I think, reused. The version I would like to propose would use a long (100km [~62 miles]) launch tunnel. The payload would ride on either a linear induction motor or an air cushion (like a really long air hockey table). An arrangement of feeder tunnels intersecting the main tunnel would allow a series of rocket engines to be used, each handing off the payload to the next like a relay baton. Phased magnets embedded in the sides and top of the tunnel could provide additonal boost. At the head end of the feeder tunnels would be circular "race tracks", where the engines would be "pre-acclerated" using a kevlar sling or a phased magnet arrangement. The operation of the system would be along these lines; an hour or two before launch time, the secondary engines would be fueled and gradually accelerated to thier pre-release speed in thier respective race tracks. Each engine would carry (WAG number, here) 10 seconds worth of fuel, and be capable of generating 3g while pushing the payload module. At launch time, one of these engines is mounted behind the payload module, and accelerates the payload up to 294 m/s. As the fuel runs out, the engine and payload seperate, and the engine decelerates (via a drag chute). Separation occurs just shy of the junction with the first feeder tunnel (1.5 km from the head end), just as the second engine is released from it's race track. As the payload module passes the junction, the second engine enters the main tunnel, already at the same speed as the payload module. The new engine then mates with the payload module and contributes 10 seconds of 3g, separating as the payload reaches 588 m/s, 5.8 km from the head end. And so it would go for 100 km, or about 8 engines. At 3 g's, payload would cover 100km in 82.5 seconds, with a terminal speed of over 2.4 km/s, or better than 30% of the 7.8 km/s needed for a circular orbit @ 185km (~100nm) (32.4% if it's alligned w-e on the equator). If fired straight up, the payload would reach a height of over 300km. If fired at a 45 degree angle, the horizontal component would be around 20% of the needed orbital velocity, and the maximum altitude without a secondary burn would be about 150km (~81nm). The orbiter would need to accelerate on its own for 193 seconds at 3g to reach orbital velocity. Contrast this with 3g x 360s for the shuttle. This is, of course, neglecting the considerable losses to air resistance. There are several advantages to a plan like this; first, an increase in payload mass doesn't have the same exponential effect on booster requirements, since you don't have to accelerate all of the first stage engines, fuel, and tankage at the same time. Second, all of the first stage engines and tankage are easily recovered. There would also be a significant increase in safety, since the abort process would be a lot easier throughout most of the initial boost phase. Other advantages include ease of maintenance (the vehicle is horizontal throughout pre-launch servicing), and the possibility of gradualy expanding the original ramp (if additional segments could be built at the head end, then the ramp could be in use while the extension was being built, but this would mean that the terminal end would have to support increasingly high exit speeds). Speaking in advance of anything approaching thorough research, it looks like most of the technology involved would be current (and some of it from the Apollo era). As for possible problems, the biggest would probably be that of traveling at >4,000 kts in atmosphere. Even if this thing where built on a mountain top, I'd expect a lot of velocity loss due to air resistance, not to mention skin heating. As I recall, the SR-71 traveling at ~2000 kts at 80,000+ ft, had some serious skin heating. In order to make this scheme work, the launch trajectory would have to have a significant horizontal component, and so would have to cut through a lot more atmosphere than a conventional boost (i.e, straight up to clear the atmosphere and _then_ add a horizontal component for orbital velocity). If anyone feels competent to hold forth on the percentage of thrust that will be needed to overcome air resistance, please speak up. One last thing; I'd like to refine the numbers a bit more, so if anyone has figures on the following, I'd appreciate it; Size & mass, Max thrust, and Isp of an SSME and the big F1 engines off the Saturn V. Relative tank/fuel (LOX and LH2) mass for current technology. Similar info on LOX/Kerosene engines. Launch profile for the shuttle. Ok, nomex bloomers in place, flame at will... Lou Adornato | Statements herein do not represent the opinions or Cray Research | attitudes of Cray Research, Inc. or its subsidiaries. lfa@cray.com | (...yet) ------------------------------ Date: Tue, 29 May 1990 15:14-EDT From: Marc.Ringuette@DAISY.LEARNING.CS.CMU.EDU To: space-tech@cs.cmu.edu Subject: Re: booster concepts Lou, I think it's definitely worthwhile to try to put as much of our launch system as possible on the ground. Power on the ground is cheap. But your proposal is much more complicated than it needs to be, and I think priority #1 should be to keep the system very, very simple. Spinning up your "relay rockets" and mating them with the fast-moving vehicle would be an incredibly delicate and tricky operation. The good news: there are a couple of easy alternatives to your relay rockets. How about just using magnetic induction to accelerate the launch vehicle? It could probably work. Another is to use the principle of the chemical gun launchers that Paul Dietz brought up last year. >"The Distributed Injection Ballistic Launcher" >H. Gilreath et. al., JHU APL Technical Digest 9(3), 1988, pp. 299-309. > >In a conventional gun, pressurized gas is injected once, and expands >as the projectile travels down the barrel. As a result, acceleration >drops off. The initial pressure is limited by the strength of the >projectile and/or the barrel. > >Ideally, a gun should maintain constant pressure on the projectile. >The DIL (approximately) does this by injecting gas behind the >projectile from the sides at points along the barrel. This is a >fairly old idea; the German V-3 guns in WWII used it (although they >were never made operational). Just as a mass driver can be thought of >as a linear electric motor, a DIL can be thought of as a linear >internal combustion engine. > >Discrete injection of gas behind a flat-based projectile doesn't work >very well. Instead, Gilreath et. al. propose to make the projectile >boat-tailed -- that is, make its base be a long cone -- and inject the >gas against the boat-tail as the projectile passes. If the boat-tail >is sufficiently pointy (small boat-tail angle theta) then the axial >velocity the gas must attain is reduced (by a factor of tan(theta)), >and the system can operate efficiently even if the projectile is >travelling much faster than the speed of sound in the gas. The limit >the authors give is about 15 km/sec. So we put a cone-shaped attachment on the back of our launch vehicle, and shoot it out the barrel of a long distributed-injection cannon. It looks like an extremely simple and robust technique. =========== In general, all of these catapult technique are limited by launcher length max acceleration max desired speed (to avoid overheating in the atmosphere). The two interesting variants seem to be 1. Launch an acceleration-resistant, long-and-skinny payload to orbit: ~1km launcher / max accel. 5000g / desired speed 11 km/s 2. Provide the first stage of a standard launch vehicle ~100km launcher / max accel. 5g / desired speed ~2 km/s I agree that the second case is very interesting. A question for y'all: just how fast DO we want our launcher to be going when it leaves the barrel? Experimental airplane data are probably the most relevant. Anybody? [ Marc Ringuette | Cranberry Melon University, Cucumber Science Department ] [ mnr@cs.cmu.edu | 412-268-3728 | "I've half a mind to be a vegetable." ] ------------------------------ Date: Wed, 30 May 90 8:57:02 MESZ From: "Joseph C. Pistritto" To: lfa@vielle.cray.com Cc: space-tech@CS.CMU.EDU Subject: Re: booster concepts The general problem I have with this is complication. Keeping all those relay rockets going would be a problem (I think). It might be more reasonable to leave the relay rockets stationary, and use them as gas generators to pressurize the entire launcher system. (Kind of like a big gun, with distributed thrust). My guess is that the rockets would have to be solids in the case, as only they would start up quickly enough (as the projectile passed). They could easily be reusable, and by having multiple instances at each 'boost point', some level of redundency would be ensured. On the other tentacle, it would probably be pretty easy to build an electromagnetic system that would provide low levels of thrust over a long period. The 'launcher' tube should probably be evacuated before hand (mostly) to cut down on airdrag losses in the tube. (A bunch of us discussed 'improving' the Iraqi gun on Bix by putting a breakable plate over the front end, and then evacuating the bore, the payload just goes right thru). Possibly the same idea could be used here. To use the 'solids' idea, you'd have to mount the solids kind of as in the following crappy diagram: +-+ +-+ +-+ |s| (solid boosters) |s| |s| |s| |s| |s| --------------- --------------------.----------------+.+----- /---------+-------+-------+\. . <--- + (Payload)|3rd St.|2nd St.| >.....--> (exhaust gasses) motion \---------+-------+-------+/. ------------------------------------------------------------- ^ +-- (thrust cone on payload, to deflect exhaust streams) actually much longer than this. Also, there'd be a set of the solid boosters on all sides of the payload. I'm thinking of solid rockets here, (because they produce a lot of high velocity gas and can be started quickly), but it's probably cheaper to use suitably burn rate limited high explosives. (after all, this is kind of what solids are anyway). Each solid stage would be burning for a very short time (shorter as the payload went faster). The angle of the thrust cone at the back would ideally be variable, but in practicality probably would have to be fixed. Perhaps this is an application for 'aerospike' designs? Would it be possible to eliminate the thrust cone entirely, and use the dynamic pressure of the exhaust gases to perform this function? Just a thought, -jcp- -- Joseph C. Pistritto (cgch!bpistr@chx400.switch.ch, jcp@brl.mil) Ciba Geigy AG, R1241.1.01, Postfach CH4002, Basel, Switzerland Tel: +41 61 697 6155 (work) +41 61 692 1728 (home) GMT+2hrs! ------------------------------ Date: Wed, 30 May 90 15:13:48 CDT From: S Schaper To: space-tech@CS.CMU.EDU Subject: Re: booster concepts Sender: mnr@DAISY.LEARNING.CS.CMU.EDU I've had a similar idea for a long time, and so have a lot of others, mine is a very long linear electric motor accelerator on the plains of Colorado and then up Spanish Peaks for example, with massive fans keeping the air pressure all the way from Abilene :-) in the tube at 10,000 to 14,000 feet pressure. The main and perhaps only problem with systems like this is the air resistance and skin heating. (so far as I know) It would work great on Luna. Another interesting place would be the Altiplano in Peru, but there are other problems there, like not enough `runway' and shining path terrorists... P. S. please keep these particulars, including Spanish Peaks, and the Altiplano my copywrited intellectual property, ie: if anything ever were to become of them, I would want some sort of credit given where credit is due... (yah right) UUCP: {amdahl!bungia, uunet!rosevax, chinet, killer}!orbit!pnet51!schaper ARPA: crash!orbit!pnet51!schaper@nosc.mil INET: schaper@pnet51.cts.com ------------------------------ Date: Wed, 30 May 90 22:44:20 CDT From: Lou Adornato To: space-tech@CS.CMU.EDU Subject: Re: booster concepts Marc.Ringuette@daisy.learning.cs.cmu.edu writes: >How about just using magnetic induction to accelerate the launch vehicle? >It could probably work. The only way I could answer that is if I dove into my college notes and tried (once again) to learn the intricacies of magnetic fields and waves. Personally, I'd rather eat bark. Fortunately, I'm sure _someone_ out there, say someone who works at a plasma and high energy physics lab, maybe even in the U.K. (I hear you breathing, Nick) could fill us in on the particulars. Lacking that, I'm sure that someone from some other accelerator-equipped lab could take up the gauntlet. Question: using current technology, how much acceleration could we expect from a big phased magnet arrangement? Keep in mind that near the terminal end, assuming a terminal speed of around 2.4 km/s and a payload module 10m long (and that's a really wild guess), the fields will have to collapse and reform in about 6.0e-6 seconds. >Another is to use the principle of the chemical gun launchers that Paul Dietz >brought up last year. O.K., I know we have some aeronautical engineers out there, anyone read the cited article? What kind of flow rates and injection velocities are we talking about? Can we generate this with conventional compressors, or will we need something like a series of shaped charges? Are the injection velocities so high that current technology can't supply an injector that can handle it (or that will have to be replaced after every launch?). While you're at it, what about the idea of a thin vacuum seal on the terminal end, to allow the boost to take place in a vacuum. I would think that the shock wave on encountering 1atm at this speed would be a lot worse than the max-q that the shuttle has to deal with. Not to mention the practical problems of trying to maintain a vacuum for 100km. I don't think either of these technologies is capable of accelerating a large mass at 3g, but perhaps taken together, this could work. One nice thing about this is that extentsions to the DIL could take place in the "breach", although I still suspect that the induction stuff will be constructed to support specific velocities, and would therefore have to be extended from the terminal end. (This is important because the longer you make the system, the more payload you send up, but the sooner you can begin operations the better the chance of funding). As far as costs for this thing go, I would guess that a good comparison would be the superaccelerating supercolider that's going to be built in Texas (or was it _around_ Texas?). Anyone know what the projected $/km is for that? I've been doing some thinking about the possible risks, and I've got one more; at the end of the boost you've got (probably) several tons of highly reactive rocket fuel traveling at 2.4km/s within centimeters of a concrete tunnel wall. A small glitch in the control of this thing, for whatever reason, is going to result in one hell of a bottle rocket. If this happens, your launch system becomes worthless for months. If you thought that the Challenger disaster was a set back, picture what it would have been like if it had taken the VAB with it. Lou Adornato | Statements herein do not represent the opinions or Cray Research | attitudes of Cray Research, Inc. or its subsidiaries. lfa@cray.com | (...yet) ------------------------------ Date: Thu, 31 May 1990 05:13-EDT From: Marc.Ringuette@DAISY.LEARNING.CS.CMU.EDU To: space-tech@cs.cmu.edu Subject: Re: booster concepts Lou writes, >What kind of flow rates and injection velocities are we talking >about? Can we generate this with conventional compressors, or will we need >something like a series of shaped charges? How about cheap kerosene rockets? Isp doesn't matter. Engine weight doesn't matter. Exhaust velocity is presumably plenty. >I've been doing some thinking about the possible risks, and I've got one more; >at the end of the boost you've got (probably) several tons of highly reactive >rocket fuel traveling at 2.4km/s within centimeters of a concrete tunnel wall. >A small glitch in the control of this thing, for whatever reason, is going to >result in one hell of a bottle rocket. I bet it's no problem at all. Artillery shells do fine, so will we. Just precisely machine the disposable metal sheath (open at the front) so that it just fits the barrel. The expanding gases might even lubricate it. I'm betting the only obstacle to the whole idea is cost: is it cheaper to build this, and build spacecraft that can handle the aerodynamic stress, and deal with the logistics, or is it just cheaper to make Pegasuses. I'm betting against this as a viable economic alternative any time soon, but I'm betting in favor of a high-g EM or gun launcher to send up bulk payloads being built within 20 years. [ Marc Ringuette | Cranberry Melon University, Cucumber Science Department ] [ mnr@cs.cmu.edu | 412-268-3728 | "I've half a mind to be a vegetable." ] ------------------------------ Date: Thu, 31 May 90 06:48 PDT Apparently-To: space-tech@cs.cmu.edu Subject: Endcapping evacuated tunnels From: Bruce Dunn It has been suggested that in any gun or tunnel type launcher that the bore be evacuated. This brings up the problem of how to seal the end of the bore, while allowing a rocket or projectile to pass out at the appropriate time. One old idea (perhaps from Arthur Clarke) is to use a lightweight plate which is held in place only by the vacuum. The bore is then not totally evacuated, but is allowed to have a little air in it. As the projectile advances in the bore, it compresses the trace of gas in front of it, gradually raising the gas pressure. When the projectile is near the end of the bore, the pressure inside the bore becomes greater that that outside, and the end plate is simply blown off the end of the tube by the higher internal pressure. This system has the advantage that pressure builds up gradually, rather than hitting the projectile suddenly as it leaves the bore. Alternatively, there is already some exotic technology available for making extremely rapid moving doors. There is a museum on the Kirkland airforce base in Albuquerque which shows details of the US atomic weapons program. In the museum, there is a display which shows how instruments are used to investigate the radiation and other emissions from underground nuclear tests. Tunnels lead from the underground test chamber to clusters of detectors. To protect the detectors, the tunnels have massive metal sliding doors immediately in front of the detectors. When the blast is set off, the detectors record the prompt radiation signature of the blast, then slam shut in fractions of a millisecond to seal off the tunnels so that the blast does not reach the detectors. The doors are presumably driven by some sort of explosive device. I am sure that a lighter weight version of the doors could easily be adapted for use at the end of a launcher tunnel. -- Bruce Dunn Vancouver, Canada a752@mindlink.UUCP ------------------------------ From: henry@zoo.toronto.edu Date: Thu, 31 May 90 11:53:02 EDT To: space-tech@CS.CMU.EDU Subject: Re: Endcapping evacuated tunnels > ... One old idea (perhaps from Arthur Clarke) is to use a lightweight plate > which is held in place only by the vacuum. The bore is then not totally > evacuated, but is allowed to have a little air in it. As the projectile > advances in the bore, it compresses the trace of gas in front of it... Unfortunately, once the projectile goes supersonic, the compression wave merges into the nose shock and the plate on the end gets no advance warning of the projectile's arrival. Either the projectile has to be able to simply punch through (as with the thin-membrane ideas) or you need faster communications between projectile and tube lid than the gas itself can provide. Henry Spencer at U of Toronto Zoology uunet!attcan!utzoo!henry henry@zoo.toronto.edu ------------------------------ To: henry@zoo.toronto.edu Cc: space-tech@CS.CMU.EDU, dietz@cs.rochester.edu Subject: Re: Endcapping evacuated tunnels Date: Thu, 31 May 90 13:11:33 -0400 From: dietz@cs.rochester.edu Unfortunately, once the projectile goes supersonic, the compression wave merges into the nose shock and the plate on the end gets no advance warning of the projectile's arrival. Either the projectile has to be able to simply punch through (as with the thin-membrane ideas) or you need faster communications between projectile and tube lid than the gas itself can provide. Or, you need a gas in which the speed of sound is large (hydrogen, say). Paul F. Dietz dietz@cs.rochester.edu ------------------------------ Date: Thu, 31 May 90 16:34:59 EDT From: Jim Meritt To: space-tech@CS.CMU.EDU Subject: use once, throw away? > Unfortunately, once the projectile goes supersonic, the compression wave > merges into the nose shock and the plate on the end gets no advance warning > of the projectile's arrival. > > Either the projectile has to be able to simply punch through (as with the > thin-membrane ideas) or you need faster communications between projectile > and tube lid than the gas itself can provide. > >Or, you need a gas in which the speed of sound is large (hydrogen, say). I wanna watch (but from a safe distance)!!! Picture this: a long tube with hydrogen in it. The hydrogen is compressed and heated by a VERY rapidly moving projectile. When the pressure and temperature of the hydrogen goes up a thousandfold it will suddenly get opened into a 21% oxygen mixture at 1 atmosphere. WWWHHHEEEEEEEEEE! And you thought the CHALLENGER flame looked good! *sheesh* Jim ------------------------------ Subject: Asteroid Prospector To: Space-Tech Mailing List Date: Thu, 31 May 90 16:21:50 MESZ From: Joseph C Pistritto Mailer: Elm [revision: 64.9] We're going to get one or possibly two flybys of asteroids during the Galileo mission, (one in 1991, another in 1993 I think). I've been thinking of concepts for a relatively in-expensive asteroid prospector mission (or maybe a family of probes) to acquire data remotely on the composition, etc. of a set of asteroids. The idea would be to use a common 'bus' from some already existing probe, possibly a flight spare, and equip it with some instruments for determining the composition, size, mass, density, etc. of an asteroid. Sort of like the ill-fated Soviet Phobos probes. We could carry along a lander if that's convenient, or maybe several, along the lines of the 'hopper' design of the Phobos units. Questions: 1) what instruments would we want? Various people have suggested using a laser & spectrometer to due surface analysis without landing. We obviously need a color camera to get glitzy PR photos. What else? 2) are they any other missions (particles/fields, etc.) that a probe running around the asteroid belt would be useful for? 3) what sort of 'off the shelf' stuff is available for constructing such a probe? 4) we definitely need a restartable motor for this thing of some kind. What sort of propulsion is appropriate? (possibly ion engines or solar sails?). The idea would be to aim for a probe that could be maneuvered to several asteroids in similar orbits. 5) anyone have any ideas how 'dense' the asteroid belt is? If we planned a mission to the 'densist' parts, how much delta-v would we need to get to say, a dozen different targets. (Yes, I realize this is a general question, but looking for ballparks here.) 6) does anyone think we could get something like this onto a Pegasus or some other 'lightweight' launcher? Getting a Shuttle launch seems almost out of the question. Other than the usual problem of getting a launch opportunity, I was thinking of using a moon-Mars gravity assist to reach the Belt, with some sort of use-once disposable motor to circularize the orbit out at the apogee, then use the restartable on-board system to manuever between different asteroids. -- Joseph C. Pistritto (bpistr@ciba-geigy.ch, jcp@brl.mil) Ciba Geigy AG, R1241.1.01, Postfach CH4002, Basel, Switzerland Tel: +41 61 697 6155 (work) +41 61 692 1728 (home) GMT+2hrs! ------------------------------ From: henry@zoo.toronto.edu Date: Thu, 31 May 90 14:09:26 EDT To: space-tech@CS.CMU.EDU Subject: Re: Asteroid Prospector > The idea would be to use a common 'bus' from some already > existing probe, possibly a flight spare... Unfortunately, existing probes have generally been custom-built every time (i.e. there are no standards) and the flight spares have already been cannibalized for later missions. (Magellan is largely built from spares.) Remember, the US basically has not built *any* interplanetary spacecraft for nearly a decade. Mars Observer, now in the works, is the first new start in a long time. There are Mars Observer spares, but they are already earmarked for later use -- assuming Mars Observer succeeds! -- in a lunar-polar-orbiter mission. > 1) what instruments would we want? Various people have > suggested using a laser & spectrometer to due surface > analysis without landing. We obviously need a color > camera to get glitzy PR photos. What else? There are a zillion flavors of remote-sensing instruments that would be of interest; the problem is thinning down the list, not finding things! One high-priority item would be a gamma-ray spectrometer, to do a survey of chemical content of the near-surface materials. > 2) are they any other missions (particles/fields, etc.) > that a probe running around the asteroid belt would be > useful for? Undoubtedly. There is little data from that region. Don't ignore the asteroidal relevance, so to speak, of such measurements. Whether asteroids have magnetic fields, for example, is an interesting question. Dust-particle detectors would be nice too. > 3) what sort of 'off the shelf' stuff is available for > constructing such a probe? Various bits and pieces, but unless you're willing to modify an Earth-orbit bird, no complete spacecraft. Mind you, if you're not going too far out, Earth-orbit satellites should be quite adequate. Mars Observer is basically a comsat. > 4) we definitely need a restartable motor for this thing > of some kind. What sort of propulsion is appropriate? > (possibly ion engines or solar sails?)... Advanced propulsion systems in general (a) aren't available off the shelf at all, and (b) have never been tested in space. That is, you'll be pioneering propulsion technology too. I don't know if that's a good idea. If you want something known and tested, it's hydrazine. (If you're feeling ambitious, hydrazine and nitrogen tetroxide.) > 6) does anyone think we could get something like this > onto a Pegasus or some other 'lightweight' launcher? With advanced propulsion, maybe. Without... perhaps not impossible, but payload will be gravely limited. The major maneuvers -- boost out of Earth orbit and aphelion maneuver to settle into the Belt -- will eat a lot of your mass in fuel, leaving very little for your probe. Note that if you want to use a light launcher, you can largely forget about off-the-shelf satellites. Almost all are too big. Henry Spencer at U of Toronto Zoology uunet!attcan!utzoo!henry henry@zoo.toronto.edu ------------------------------ End of Space-tech Digest #61 *******************